In his first interview since being defeated in last November's poll, the former Republican presidential nominee urged Mr Obama to stop "flying around the country and berating" his political opponents.

"The president has the opportunity to lead the nation and to bring Republicans and Democrats together," Mr Romney told Fox News. "It's a job he's got to do and it's a job only the president can do."

The former Massachusetts governor promised during his unsuccessful campaign for the White House to forge a bipartisan settlement on the future of America's economy that has eluded Mr Obama.

He spoke as the US braced for $85 billion (£56.6 billion) in public spending cuts to take effect at midnight, after Mr Obama and Republican leaders again failed to reach a budget deal in last-minute talks.

Mr Romney's wife, Ann, compared their abrupt exit from public life after the election loss to their experiences of the hierarchy of the Mormon church, in which Mr Romney was once a senior cleric.

"In our church, we're used to serving, and you can be in a very high position, but you recognise you're serving," Mrs Romney said. "And now all of a sudden, you're released and you're nobody."

On her husband's campaign she said: "It was an amazing thing, and it was really quite a lot of energy and a lot of passion and a lot of people around us... and all of a sudden, it was nothing".

Mr Romney added: "We were on a roller coaster – exciting and thrilling, ups and downs. But the ride ends, and then you get off. And it's not like, 'Oh, can't we be on a roller coaster the rest of our life?' It's like, 'no, that ride's over'."

After almost six months spent recuperating at the couple's beachside mansion in La Jolla, California, Mr Romney will next month return to the political spotlight by delivering a speech at CPAC, the annual conservative convention.

It emerged this week that he had quietly donated thousands of dollars to the re-election campaign of Chris Christie, the New Jersey governor, whom he shortlisted for last year's vice-presidential spot.

Mr Romney criticised Mr Obama for remaining in campaign-mode rather than working harder to forge an agreement to prevent the $85 billion cut, a so-called "sequestration" that was designed to be so unpalatable that leaders from both parties would be forced to agree another deal.

"No one can think that that's been a success for the president," he said.

"He didn't think the sequester would happen. What we've seen is the president out campaigning to the American people, doing rallies around the country, flying around the country and berating Republicans and blaming and pointing."